The present invention is directed to a container, such as a box, with folding or collapsible sidewalls and in particular to a container having reduced outward deflection and reduced vertical sag. Cross-reference is made to commonly assigned U.S. patent application Ser. No. 07/845,121, filed Mar. 3, 1992, incorporated herein by reference.
A number of containers having hinged or otherwise collapsible sidewalls have been proposed, since collapsing sidewalls provides the ability to reduce the volume required for such containers during storage or initial shipment and, for reusable containers, during return-shipment. Containers of this type, however, have often been subject to certain problems or deficiencies. In some configurations, there has been a tendency of the containers to experience a vertical downward deflection near the center of the sidewalls (or base) or xe2x80x9csagxe2x80x9d over time. This has been especially pronounced in certain configurations designed for stacking containers vertically one on top of the other. Such sag makes it difficult to efficiently pack containers into a limited space and contributes to material fatigue, eventually leading to failure of the container. Some previous devices have attempted to diminish the sag effect by adding reinforcing beams across the lower surface of the container. However, such beams have often interfered with providing the capability of four-way forklift entry since such beams typically run transverse to the path of forks of a forklift along at least one direction of entry.
Another troublesome type of deflection has been outward sidewall deflection. Use of the containers to transport dense loads results in outward forces being applied to the sidewalls and some amount of deflection often results. This deflection interferes with efficient packing of containers into a confined space. In some applications, containers are designed so that an integral number can be efficiently, (i.e., tightly, with no wasted space) packed into a larger vessel such as the hold of a cargo ship, a trailer, an airplane, etc. However, if the sidewalls of such containers have experienced deflection and, for example, undergone xe2x80x9cballooning,xe2x80x9d such containers will no longer pack correctly into such defined spaces. Furthermore, if containers are subject to sidewall deflection, even if containers have been successfully packed into a larger vessel, if sidewall deflection occurs after such packing, the containers may become tightly jammed into the larger vessel and it may be difficult to extract such jammed vessels.
In some instances, containers are provided with a removable top or lid, e.g., to protect the contents of the container during shipment, storage, etc. Previous lid devices have often been incompatible with container stacking such that containers were designed to stack in an unlidded condition, or to stack in a lidded condition, but not both. Previous lids with a stacking capability were sometimes susceptible to formation of pools if subjected to water, such as rainwater. Many previous lids added a significant amount of height to the container, particularly if the lids were configured to accommodate stacking. A number of lid designs were useful for storage but were subject to accidental loss during shipment, e.g., by the force of wind acting on the lids.
In some cases, it is desirable to provide one or more doors within one of the collapsible sidewalls to facilitate removal of the container contents. Previously, it has been difficult to successfully locate a door in the lower portion of a sidewall which is designed to swing outward and upward. The design was particularly difficult when the container was intended for bulk transport (i.e., transport of a large number of discrete and loose or unrestrained items, e.g., loose bolts, washers, etc.). In this application, a large amount of force is applied to the door and it has been difficult to design such a door that will successfully withstand the force without failure or undue deflection.
Previous devices have also been subject to deflection of the bottom surface or floor of the container. Some previous designs have provided for ribbing extending downward from the flat floor surface of the container. However, previous devices have required an excessive amount of ribbing to achieve acceptable strength and stiffness contributing to additional weight and cost of the container.
According to the present invention, a number of features can be used to reduce or eliminate vertical sag in a container. One feature is a particular reinforcement or ribbing pattern on the base portion of the container. The ribbing pattern used on this embodiment includes a plurality of ribbed regions extending from the central portion of the base of the container radially outward and, preferably, includes four regions in an X-shape extending from the central area of the base to the corners of the base. In one embodiment, there is substantially no ribbing in the interstices between the arms of the X-shaped structure.
Another feature which assists in reducing deflection involves a hinging arrangement which allows the sidewall to be pivoted downward to a collapsed configuration. According to this embodiment of the invention, when the sidewall is in an upright configuration, there is an engagement between a lip extending downward from the sidewall and a lip extending upward from the rim of the base. The base lip is positioned outside the sidewall lip so that outward force on the sidewall is transmitted to the base rim. Preferably, the sidewall lip and the rim lip are substantially continuous along the entire span of the lower edge of the sidewall. The hinging arrangement between the sidewall and the rim is configured so that there are no substantial interruptions of the sidewall lip and the rim lip, even at the location of the hinges. This is believed to avoid an undesirable concentration of forces at stress points.
A further feature useful in reducing deflection involves a rib pattern on the surface, preferably the outside surface of the sidewalls. In this embodiment, the ribbing pattern includes one or more curved, closed-shape ribs, preferably, circular ribs, with a plurality of linear ribs connecting to and radiating therefrom. This configuration is believed to provide a higher stiffness and reduced deflection of the sidewalls.
The present invention also includes a container having a door in one or more of the sidewalls. In this embodiment, the door is in the lower portion of the sidewall and extends from the lower edge of the sidewall upward, but without extending to the upper edge of the sidewall. Preferably, the door is hinged so as to open upwardly and outwardly and has one or more latches coupling the door in the closed configuration, to the base of the container, preferably to a shear plate structure in the base of the container. In one embodiment, outward forces are transmitted by the door to the base of the container.
In one embodiment, the door is held in the open position by a slam latch which is configured to engage the door when the door is slammed into the latch. Preferably, the door can be disengaged by suddenly pulling or jerking the door outward and downward away from the slam latch. In one embodiment, these features are achieved by the angular configurations of a jamming surface and a retaining surface of a slam latch and the resilient nature of the slam latch.
A further aspect of preventing unwanted deflection includes the positioning of ribs in the base of the container. According to one embodiment, the base of the container has an integral planar surface and ribbing attached or, preferably, integral with the planar surface. The ribbing, in this embodiment, extends upward from the planar surface, i.e., in a direction towards the interior of the container. When it is desired that the container should have a flat interior bottom surface, a plate can be positioned on top of the ribbing. Preferably, the base of the container is provided with nine points or regions of support, including support regions at the four corners, support regions at the centers of the four sides and a central support region. This configuration provides for desired support without interfering with accommodating the forks of the forklift.
Preferably, the containers can be stacked one upon the other, either in collapsed positioned, uncollapsed position, with or without a cap or top. When a cap or top is used, preferably the cap or top has a convex or dome shape on the upper surface to avoid pooling of water. In one embodiment, a rim is formed in the upper surface of the cap or lid and, preferably, the rim is provided with one or more channels to avoid pooling of water. The tops or lids can be configured to add on a small amount of height to the overall stack, such as about xc2xc inch per container. Preferably, the lids include detentes to grab the rim of the containers so as to avoid blowing off or other unwanted removal.